Todo List

Core:
 - Finish table and shorthand CSS attributes
    - border-collapse, caption-side, empty-cells, table-layout, vertical-align
    - background
    - border, border-*
    - font
    - list-style
 - Implement all non-essential attribute transforms
 - Microsoft Word HTML cleaning
 - Plugins for major CMSes

Code issues:
 - Massive profiling, make it faster!
 - Make URI validation routines tighter (especially mailto)
 - Distinguish between different types of URIs, for instance, a mailto URI
   in IMG SRC is nonsensical
 - Factor out Host validation to its own AttrDef
 - Rewrite table's child definition
 - Silently drop content inbetween SCRIPT tags

Enhancements:
 - Do fixes for Firefox's inability to handle COL alignment props (Bug 915)
 - Pretty-printing HTML